The present disclosure relates generally to gas turbine engine exhaust cases. More particularly, the present disclosure relates to design and construction of fairings that fit around and protect ring-strut-ring structures.
Turbine Exhaust Cases (TEC) typically comprise structural frames that support the very aft end of a gas turbine engine. In aircraft applications, the TEC can be utilized to mount the engine to the aircraft airframe. In industrial gas turbine applications, the TEC can be utilized to couple the gas turbine engine to an electrical generator. A typical TEC comprises an outer ring that couples to the outer diameter case of the low pressure turbine, an inner ring that surrounds the engine centerline so as to support shafting in the engine, and a plurality of struts connecting the inner and outer rings. As such, the TEC is typically subject to various types of loading, thereby requiring the TEC to be structurally strong and rigid. Due to the placement of the TEC within the hot gas stream exhausted from the turbines of the gas turbine engine, it is typically desirable to shield the TEC structural frame with a fairing that is able to withstand direct impingement of the hot gas stream. The fairing additionally takes on a ring-strut-ring configuration wherein the struts are hollow to surround the frame struts. The structural frame and the fairing can each be optimized for their respective functions, such as load bearing and temperature capabilities.
Conventionally, manufacture of a TEC has involved casting the ring-strut-ring frame as a single piece and separately producing a ring-strut-ring fairing. Typically, the frame is separated into a plurality of pieces, reassembled in-place with the fairing, and welded or bolted back together. Historically, it has been simpler to reassemble the frame within the fairing in order to protect the structural and aerodynamic integrity of the fairing. However, separating the frame into pieces inherently produces structural weaknesses that may degrade performance. There is, therefore, a need for improved manufacturing and assembly processes for turbine exhaust cases.